Self-reversing power jack



June 21, 1949. BRASSELL 2,473,566

SELF-REVERSING POWER JACK Filed April 4, 1946 3 Sheets-Sheet l INVENTOR.BRYAN BRAS- s 5;}, L

ATTORNEYS June 21, 1949. s. BRASSELL SELF-REVERSING POWER JACK 3Sheets-Sheet 2 Filed April 4, 1946 L Y ai 0W n T E MS m ms r w A m B N Ay W a B i w A m t .1. l /J wv Y/l w u. a .m 2 a A v- Patented June 21,1949 UNITED STATES PATENT OFFICE 18 Claims.

This invention relates to power transmitting apparatus and mechanicalmovements, and more particularly to motion converting mechanism.

One of the objects of my invention is the provision of reliable andhighly satisfactory motion converting mechanism which eiliciently andreadily effects the conversion of rotary motion to linear motion.

Another object is the provision of power transmitting mechanism wherebyunidirectional rotation from a source of motion is readily andeffectlvely transformed into linear or reciprocatory action.

A further object is to provide mechanism of the character referred towhich is simple to install, and which is well calculated to serve undermany different conditions of actual practical use.

Another object of my invention is the provision of power transmittingapparatus, as for example a power transmitting system, including andutilizing motion converting mechanism of the character noted.

A still further object is the provision of rotary to linear motionmechanism capable of simultaneously developing multiple rotationscontributing to the achievement of quick strokes of linear movement.

A further object is to provide efficient and practical mechanism forautomatically converting rotary motion to reversing strokes orreciprocation, all with minimum stress on working parts during reversalof any given stroke.

Otherobjects in part will be obvious and in part pointed outhereinafter.

My invention therefore consists in the combination of elements, featuresof construction and arrangement of parts, as described herein, the scopeof the application of which is indicated in the following claims.

In the accompanying drawing illustrating certain features of myinvention:

Fig. 1 depicts an embodiment of the rotary to linear or reciprocatorymotion converting mechanism in sectional elevation;

Fig. 2 represents, in elevation, the same apparatus as in Fig. 1;

Fig. 3 is a horizontal section of the mechanism taken substantially onthe line 33 in Fig. 2;

Fig. 4 is a fragmentary view of certain rotative and reciprocativelements represented in Fig. 1;

Fig. 5 presents in detail a form of joint for transmitting rotation andreciprocation;

Fig. 6 depicts, in elevational view, a modified form of stroke selectormeans of the conversion mechanism;

Fig. 7 is a sectional elevation corresponding to Fig. 6;

Fig. 8 is a fragmentary view of certain detent mechanism of the modifiedstroke selector means;

Fig. 9 is a view, in elevation, representing modified unidirectionalrotary motion transmitting means of the rotary to linear orreciprocatory motion converting mechanism;

Fig. 10 is a fragmentary sectional elevation of certain elementsrepresented in Fig. 9; and

Fig. 11 schematically represents a power transmitting system including arotary to reciprocatory motion converting mechanism.

Similar reference characters designate corresponding parts throughoutthe figures.

As conducive to a clearer understanding of certain features of myinvention, it may be noted at this point that mechanisms for convertingrotary motion to linear motion have come into widespread demand for suchpurposes as in the pumping of fluids, in tooling and machiningoperations, for the steering of craft, in operating power presses andhoists, and. for a great variety of other uses including those in whicha linear mechanical movement as derived from rotary motion is dependedupon to set related equipment or transmit linear impulses to the same.While there are quite some few rotary to linear motion mechanisms in theprior art, many of these are open to such objections as being difficultof control during use, particularly as regards the achievement ofsatisfactory and reliable reversal of strokes or continuation of anarrested stroke, for making up the linear movement. Then too, certain ofthe prior art mechanisms are not readily adaptable to receiveunidirectional rotary motion from a suitable source of power and convertthe same to linear motion. Still other heretofore known motionconverting mechanisms lack efiiciency and positiveness of mechanicalaction. In other instances mechanisms are so mechanically complicatedand space consuming as to render installation inadvisable.

An outstanding object of my invention accordingly is the provision of asimple, compact and reliable motion converting mechanism wherein atransition from unidirectional rotary motion to reciprocatory motion ispositively and efiiciently achieved under highly satisfactory conditionsof reversing or alternating the stroke of reciprocation.

Referring now more particularly to the practice of my invention,attention is invited to Figs. 1 and 2 of the drawings wherein there isrepresented a motion converting mechanism, generally indi- 3 cated bythe numeral ID. This illustrative mechanism of my invention includes asuitable casing l I, through which there extends a drive shaft l2, thelatter being journalled as in bearings i la, I lb, and illustrativelyforming an included part of selectively operative means for transmittingunidirectional rotation to either of oppositely disposed co-axial gears2| and 23 of epicyclic or differential gearing. Two gears, 14 and I5,and an intermediatelypositioned sleeve I6 are mounted on the shaft.Thegears' just mentioned are capable of idling, and of becoming drivinggears when engaged into service by selective movement of sleeve it whichis splined to the drive shaft'in' such fashion as to be free forlongitudinal movement to locking engagement with the'respective' gears.Selection means, for example including a cam follower, is employed forimparting longitudinal motion in either direction to the sleeve thus toengage either gear- [4 orgear l5 and lock the same tothe d'ri've'shaft.The cam follower conveniently is a centrally perforated metal disc- ITreceived on sleeve I6 and free for rotation between collars I8fixe'd tothe sleeve.

The gears M and I fi'rnesh in power transmitting relation withcorresponding gears 28' and 29 (Figs. land 2) which'are' fiiiedtorespective ones of sleeves l9 and 2'0, co-axially'telescoped forrelative rotation. The sleeve l9-' is-"supported in bearing l lc in thewall ofcasing H, and extends into gear bOX'ZZ through be'aring- 22) ofthe latter. Sleeve 20, on the'other hand;conveniently passes through thegear box, through bearing: lid in the casing wall,andco-airiallysupportscollar 3B J'ournalled in bearing 22-!) "ofthe gearbox.

The bevel'gears-zl', 23"in' the gear box are connected'for rotating'with the correspondingsleeves l9 and 2d; the collar 38, gear 23 andgear 28 conveniently being integral and keyed to shaft 20 asaunit.Pinions-26and 2'! carried by spider means, illustratively ineludin'g'the gear b02522 and stub shafts 26a, 21a, join' the bevel Z! and 23'thereby forming with the same" an epicyclic or differential gear.

The apparatus"ofthe'mechanism thus far described is conveniently tracedfrom a suitable source'of power, as for example an operating electricmotor which-drivesthrough a belt'and pulley system 24 soas to" impartclockwise rotation (as denoted by arrow'in Figs; 1- and 2) to the driftshaft 1-2; Assuming the'ge'ar M to be locked tothe drive shaft and gearl5 to be free of the clutch sleeve a's shown; a" counter-clockwise rotation' is'tr'ansniitted through the power take-off gear 28to-'sleeve-'2tl and bevel gear 23 of the differential gearing. With thegear box restrained against rotation'on" bearings 22); 229, as by stopmechanism to be described hereinafter, the bevel gear 23 drives pinicjns26 and 21, thus imparting a clockwise rotationtotlie bevel gear 2-! andalso to the related sleeve [Sand gear 29. The motion from'gear 29 isreceived-by the'meshing idler gear IS. The circumstances ass-ur'ned,-therefore; are such that'the-s-leeve [9- rotates in a clockwisedirection and the co axial sleeve '2 t rotates counter-clockwise.

With" the drive shaft l-2 still rotating in the clockwise direction asbefore, and assuming the gear box to be held against rotation, but withgear l5 engaged by the clutch sleeve and gear [4 free of the sleeve, thegear 29 transmits a counter clockwise rotation to s'leevel9- and therelated bevel 'gear 2|. This rotation is'rever'sedthrough pinions-ZG andZhthe-bevelgear 23', sleeve Zllandgear ZB'aZccQrdin-gly rotate inaclockwisedirection.

Motion from gear 28 is received by gear [4 which now is an idler gear.

It will be seen that a general eiiect of operating the drive shaft in aconstant direction of rotation and alternately selecting one of thegears l4 and I5 as the driving gear, is that of alternately rotating thesleeve [9 in one direction and then in the other while sleeve rotates inthe opposite direction. This same effect, I find, is a highly usefulmeasure in converting rotarymotion of the drive shaft l2intb'recipiocatorymotion. In the present embodiment, sleeves l9 and 20are simultaneously utilized for rotating threaded rods and threadednut's'in oposite directions and, alternatively, in reversed oppositedirections, as for example, threade'd'cylindrical rods SI, 32 and nuts26a; 3541,3522 and 36a, to produce reciprocation. The rods 3|, 32 aredisposed in co-axial relation to the sleeves. The rod 3|,illustratively, is considerably larger in diameter than rod 32. Bothrods have'r'i'ght han'd threa'dedse'ction's and left hand threadedsection's along the cylindrical surfaces thereof, the rig'ht handthreads being indicated by reference-characters 3Ia, 32a, and the Elleft hand'threa'cls' by 3'), 32b. There is a union or spline 33 (Fig; 5)connecting thethreaded shaft ends for relative longitudinal'movernentand for rotation as a unitary shaft. conveniently includes a groovedsection 320 of the rod'32, and a bored' and internally featheredsectiontlc of rod 3| into-which the grooved section telescopes and'fits. Asimilar connection is established by joint 34, in which the rod 31 issplined to sleeve IS for rotation therewith yet is free-for longitudinaldisplacement relative to the sleeve.

Each threaded section of the rods is in operativeengageihent witha'correspondingnut'wliich rotates with the power receiving sleeve 22'].In this sense, threaded section 3lb accommodates the" nut 20a,.whichconveniently also forms an end of the power receiving sleeve 29 and isfixed-in longitudinal-positionalongwith the rest of the sleeve as by thejournal in bearing The remaining nuts 35a on threaded section 3|a, 35bon section 32b, and nut" 36a on section 32a, are feathered for ridinglongitudinally in grooves 28 (represe'ntedby dotted lines-inFig. 1) inthe inner surface'of sleeve' 20. By suitable means, the nuts 20 and aclockwise rotation to sleeve I 9; providedthe gear box 22 isrestrained.Thus, under these conditions, and with therods' and nutsoi the linearmotion mechanisr-ri'ready'to-begin a stroke from the lower strokeposition represented in Fig. 1, the power receiving sleeve 210' rotatesall of the nuts 20a, 35a; 35b aridtta', in a counterclockwise direction;The" threaded rods 3i and 32, on which the nuts rotate, are themselvesrotating,- this being in a clockwise direction determined by theclockwise motion of the power receiving sleeve retransmitted throughjoint 3% between the sleeve and rod and through union 33 between therods. There ensues a highly positive and eflicient displacement whereinthe The unfair; or jointt longitudinally fixed, but rotating nut 20aacts with threaded section 3171 of the oppositely rotating rod 3| toelevate the latter to the completed upper stroke position represented inFig. 4. This upward displacement is possible in view of the spline typeconnection 34. Meanwhile, nut 35a is carried upward the distance con--tributed by the action of nut 253a, and by engagement andopposedrotation with the threaded section em on the rod is driven upward afurther amount corresponding to the threads traversed on the rod. Sincenuts 35a and till) are held a constant distance apart and arerespectively mounted on the rods 3i and 32, the upward movement of thenut 35a is transmitted to nut 35b and the corresponding rod 32. The rod32 accordingly slides up as permitted by the union 33. In addition, therelative rotation of nut 5th and threaded section 32a advances rod 32farther upward by an amount corresponding to the threads traversed. Theupward advancement of the rod 32 meanwhile is accompanied by the Hspective clockwise and counter-clockwise rotations of threaded sections3m and nut 353a, which serves to elevate the nut and the relatedreciprocatory motion member 3b to top stroke position represented inFig. 4. A coupling, including arm 38 adapted for idling in ball and cagebearings 39, is convenient for transmitting the longitudinal stroke ofmember 36 to reciprocative member iii without transmitting any rotationof the sleeve.

Upon driving the reciprocatory motion member .35 to top stroke position,the power receiving sleeves l9 and 2d are reversed in rotation promptlyby shifting the clutch sleeve it from gear i i to coupling engagementwith gear 15 and still maintaining clockwise rotation of the drive shaftI usually achieve this shifting action by automatic selector meanssynchronized with stroke of the reciprocatory movement, and preferabiythrough freeing the housing of the differential gearing for rotation atthe proper time, and relying upon the ensuing movement to effect theshift. Conveniently, for this purpose, a slide ii extends throughopposite side walls of the casing I l and presents a bracket Ma forengaging buffer spring loaded detents 22a, 22b, 22c and 22d uniformlyspaced on the circumference of the c i drical housing of gear box 22 andprotruding from the wall. A cam path or groove 22c in the housing of box22 (Fig. 2) receives the cam follower ll and has a sweep sufficient toshift the clutch sleeve IE on drive shaft l2 from driving or lookingconnection with one of gears Hi and i5 momentarily to interlockingengagement with both gears and then to driving engagement with the otherfor each quarter revolution of the housing. For synchronizing theinitiation of the camming action just mentioned, with completion ofstrokes in the reciprocating movement of sleeve 36, there are suitablyspaced stops Mb, tic fixed on the slide ii on opposite sides of arm 38.

It will be appreciated that by rotation of the differential gear as aunit while reversing any gear stroke of the reciprocatory movement, thethreaded rod and nut combination is immediately relieved of relatedrotation and remains in neutral until the shift is completed. Thisenables accurate control over length of stroke of the reciprocatingmovement. Further the shifting of stroke direction is achieved withminimum stress since the rod and nut mechanism is not under working loadonce the differential gearing is released for rotation as a unit.

In the. present instance of operation let it be assumed that the gearbox housing is held against rotation by detent 22a resting on bracketlla just before completion of the up stroke of sleeve 36. The sleeve inmoving upward contacts stop llb thus carrying bracket 4 l a free ofdetent 22a. This frees the differential gear box for rotation, underwhich conditions bevel gears 2|, 24 and pinions 26a, 21a rotate as aninterlocked unit all in the same direction with the power receivingsleeves l9 and 20 momentarilyunder the action of driving gears M, l5 andgears 28 and 29. Since the drive shaft I2 is rotating clockwise, thesleeves l9 and 20, differential gearing, and gear box 22 all rotatecounter-clockwise substantially as a unit until detent 221) contacts thebracket 4 la. The rotation sweeps cam follower ll along path 22c andconsequently sleeve l6 into engagement first with both gears l4 and I5,and then with gear l4, and meshing gear 28 now becomes the driving gear.As already described, the gear 5 for clockwise rotation of the driveshaft imparts a counterclockwise motion to sleeve I9 and a clockwiserotation to sleeve 20. Under these conditions the threaded rods 3! and32 are driven clockwise and he corresponding threaded nuts are drivencounter-clockwise This action serves to return the rod 35 through thelongitudinally fixed and rotating nut 2M and joint 34 to lower strokeposition represented in Fig. 1. The downward displacement carries nut35a down a corresponding amount, and by engagement and opposed rotationwith the threaded section 3| a travels down the rod to lower strokeposition, also carrying along the nut 35!; as permitted by union is. Thelatter nut contributes in lowering rod 32 by travelling up threadedsection 32a. As the rod 32 is lowered, nut Mia and member 36, arm 38 andreciprocative member it also are lowered. A further lowering action isproduced by the nut 36a, by virtue of relative rotation with the rod.

Simultaneously with the reaching of lower stroke position, arm 38 forcesdown lug 41c and bracket Ma, thereby freeing detent 22b and consequentlythe gear box 22. Since the drive shaft i2 still is rotating clockwise,the sleeves l9 and 2% the differential gearing, and gear box 22 oncemore rotate counter-clockwise as a unit, this time,

until detent 220 contacts the bracket Ma. The rotation sweeps camfollower I! along path 22c, thus bringing sleeve Iii into drive shaftcoupling relation with gear l5, which then drives the mechanism throughan up stroke of reciprocatory motion in a manner already noted.

The Figs. 9 and 10 illustrate a modified drive for operating the sleevesi9 and 2!] in opposite directions and at different speeds thus to drivethe threaded rod and nut arrangement more rapidly in one direction ofstroke as compared with the opposite direction. The modificationincludes drike shaft l2 and related mechanism for transmitting powerfrom a suitable source into the casing ll. There is a small gear l4 onthe shaft in low speed gear train with relatively large gear 28; alsolarge gear i5 is on the shaft in high speed operating connection with asmaller gear 29. The gears 28 and 29' illustratively are substituted toperform at different speeds the described functions of gears 28 and 39.I employ a sleeve i6 splined to drive shaft l2 for alternately couplingthe gears M, iii to the source of power, while the other is released foridling. The sleeve illustratively includes friction plates l6'a, Hib foreffecting the desired coupling through either of corresponding frictionsurfaces M'a, l5a of the gears. A suitable cam follower il, in bearingsl8 emanate onthe. sleeve,:ridessin:cam pathl! 2a of the gearbox 22 for.alternatelydisplacing thesleeve 'ItO locking engagement withithe ;gearsM" and l 5 to reverse the rotations of :sleeves -'|'9:and 220'.

:In Figs. 6, 'Land181thereisrepresented-a modified .form of powerconvertingmecihanism which instead of depending .uponlthe simultaneousoppositerotation of;thr.eaded.nuts.;and threaded rod means for producingreciprocation, achieves the reciprocatory motion Withsa diiferentia'lgear and sleeves 1.9 and :20 as before, but by the alternate proceduresof..holdingfithecrelated=nuts 20a, 35a, 35b and 36a (Fig.1) .-:againstrotation while rotating the threadedrods 31I.,-'32, and rtating the nutswhile holdingxthe rods. "This-sequence of operations is effectively. and:efiiciently performed by alternately restraining. the sleeves 19 :and'20 against rotary ;motion' while .driving: the gear itselfin.aaconstant direction ofmotationas the motion transmitting means which:is selectively :op-- erativewith .the differential-gearing. The sleevesillustratively support respective levers 49 and 50, which extend:laterally :in:opposite directions and co-iunction with :detents ill and352, respectively, for stoppingtheindividualsleeves. Adetent carriageincluding frame members 253, 54 which support the .detents 154,..52 .at:opposite. ends thereof to form a substantially. mectangular frame, -isaxially .hinged at 53a, 54a :for rotation by means ofarm :55. Thedetent5| comprises two substantially parallelholts 5-la.:.C-Eig;- 8.)interconnecting the frame membersl53 .and54. Each bolt 'accommodates asleeve :51 b, =which is equipped with a fixedlug 51c and .isadapted forslidingmovement against the action 'of a buffer spring 51d. The lugsonthe sleeves are adjacent, and jointly present a surface for receivingand=holding lever 49. 'Detent 52 'isof similarconstructlon and isadapted for receiving -and' -holding the -lever '50 against rotation.

To reverse the stroke of reciprocatory motion developed by driving thegear box '22, "the diiTerential 'gearingtherein, and 'sleeve +9 =whil'eholdingsleeve 'by lever Hand'detent 51;,the detent carriage isrotated-toengage'lever 510 on sleeve f9 with detent 52. This serves to releaselever '49 from 'detent "5.1 and consequentlyfrees the sleeve 20ior'rotation. momentarily, there 'is a unitary rotation of sleeves5.9;20 and "the differential gear, all in one directionby .virtueoicontinualunidirectional driving of 'thehousingjof gear'box2'2" in thedirection indicated'by.arrowjinl lig. .8. .Thus, lever 50 engages detent5.2.,thereby restraining sleeve l5, and leaving. sleeve 20 .free forrotation under power from therotatingbox 22 and diflerential gearingtherein. Therotationof'sleeve 20 reverses the stroke .of reciprocation.A.further reversal of stroke :is indicated by positioning the detentcarriage to engage-lever and-tdetent '51. and free lever 50 and detent52. .With'lever :50 free, there is once moreannitary .rotationof sleevesI9, 20 and .thedifierential-gear,.all-in one direction, assumingcontinued unidirectional driving of the gear box 22'. Theleverdfl thenstrikes detent 5 l, whereby further emotion. of. sleeve 2-0 is arrestedand rotation. .ofxsleeve i9 continues throughout:thesreversedstroke.

.In automatically. operating the :motion converting mechanism of thepresent embodiment, the appropriate detentJB I l5-2'ziszswung to lockingengagement with its .correspondingflever .49, i5fl under forcetransmitted'afromisleeve 36, arm 38 and lug 4 b or-4'lcandthrough'slidefl lito arm 55. This linkage is so adjusted: as toalternate the holding and release of levers iiiand 50, therebyalternately reversing the stroke of sleeve'31.

Referring to Fig. 11 of thedrawing, 'there is illustrated a formof-power transmitting system in accordance with my invention. In'thesystem, a suitable motor BIJ-is connected for 'opera'tinga reciprocativepump in well=65 through one of my motion converting mechanisms I'llconnectedby means of reciprocative member 40 through 'well derricklinkage to'pump shaftB'S. 'Thewellderrick is equippedwith .an upstandingframe 5'] which supports a pumping arm 62, fulcrumed at 61a andconnected atone end--to=the=pump shaft 66. A roller -63 connected in anarticulated joint between adjacent ends of link-64 and reciprocativemember 40 is guided in track 61. 'At opposite end, the link :64 ishinged to the pumping arm 5-2 and is of such length andso guided'by'the'roller 63 as to transmit-an up and a down stroke to the pumpingarm, and consequently to the'pump, for each single stroke from themechanism 4 0.

It will be appreciated that'while the mechanism for-converting rotarymotion, as hereindescribed, is highly suited for the output ofalternately reversedstrokes of reciprocation of constant amplitude, themechanism'may benrevers'ed *asdesired along the length of any givenstroke, as'by manual or automatic control applied to slide M '(Figs. '1and 6) or may be stopped and 'started oncemore, to continue in a givendirection, as byrstopping the drive 2:3 and then resuming the driveinthesame-direction as before.

While two telescoping threaded rods have been described forcoaction'with threaded nuts .for achieving reciprocatory motion intherembodiment hereinbefore set :forth, it will 'be understood that asingle threaded rod may be semployedsin conjunction with one or morenuts for coacting therewith for producing linear motion orreciprocation.

Since many possibleembodimentsmay be made of my invention andsince manychanges may be made in the embodiments'hereinbefore set forth, it willbe understood that all matter described herein, or shown in thedrawings,.is to be interpreted as illustrative and not as a'limitation.

I claim:

1. In mechanism for converting rotary motion to reciprocating linearmotion, the -'combination which includes, motion converting meanscomprising at least two engaging threaded members mounted for relativerotation and co-action "to produce linear-displacement'of=one of them,gearing means connectivewith-saidthreadedmembers for transmittingopposite driving rotation to the same to direct thedisplacement, andmeans controlledby movement of said menibertoreverse the direction ofrotation-of both' said members.

2. In mechanism for convertingrotary motion to linear motion, thecombination which-includes, motion converting means lcomprising atleasttwo engaging threaded-members mounted for relative rotation andco-action to 'produce linear displacement of at least oneof them,differential gearing having a pair-of difierentialgears .eachiconnectedfor rotation with one :of' :said athreaded :members, andmeans forselectively coupling :the differential gears to rotary drive means :of.fixeddirection .rotation.

3. In mechanism for converting :rotary :motion to reciprocatory motion,.the icomhinationrwhich includes, motion converting means. :comprising:at least two engaging threaded :members mounted for relative rotationand co-action 'to produce ;re-

7 .ciprocation :of 0118 of them,;sdifierential gearing 9 havingcorresponding gears thereof connected for driving the corresponding onesof said threaded members, and means for alternatively coupling saidcorresponding gears to a rotary drive source of fixed rotation, and apinion between said corresponding gears mounted on a normally fixedaxis.

4. In mechanism for converting rotary motion to reciprocatory motion,the combination which includes, motion converting mechanism comprisingat least two engaging threaded members mounted for relative rotation toproduce displacement of at least one of them, mechanism forsimultaneously transmitting opposite rotations to said threaded membersto achieve the displacement and means dependent on the amount of saiddisplacement in either direction to reverse the direction of saidrotations.

5. In mechanism for converting rotary motion to reciprocatory motion.the combination which includes, motion converting mechanism comprisingat least two engaging threaded members mounted for alternately reversedopposed rotation to produce reciprocation, drive means operating in aconstant direction, means connecting said drive means for alternatelyrotating said threaded members in opposed directions, and gear means forinterconnecting the threaded members in opposed rotary relation duringoperation of said drive means.

6. In mechanism for converting rotary motion to linear motion, thecombination which includes, dilferential gearing, unidirectional rotarymotion transmitting means selectively operative with said differentialgearing for driving through opposite sides of the same, and two memberseach connected for simultaneous rotation with one of the opposite sidesof said. differential gearing and mounted for co-action to producelinear displacement.

7. In mechanism for converting rotary motion to linear motion, thecombination which includes, differential gearing, unidirectional rotarymotion transmitting means selectively operative with said differentialgearing for alternately driving through opposite sides of the same, atleast two engaging threaded members each rotatable with one of saidopposite sides of the differential gearing and mounted for co-action toproduce linear displacement, and selective means actuated by movement ofone of said threaded members for engaging said unidirectional motiontransmitting means to driving reiation alternately with one or the otherof said opposite sides of the differential gearing thus for producingreversed strokes of reciprocation with said threaded members,

8. In mechanism for converting rotary motion to recipricatory motion,the combination which includes, differential gearing comprising opposedgears and at least one interconnecting pinion for the same,unidirectional rotary motion transmitting means selectively connectivewith the differential gearing alternately through said opposed gears, atleast two engaging threaded members rotatable each with one of theopposed gears of the differential gearing and mounted for coaction toproduce reciprocation, and selector means for automatically setting saidunidirectional motion transmitting means to driving relation with thedifferential gearing alternately through said opposed gears thusproducing alternately reversed strokes of reciprocation with saidthreaded members, said selector means including means for restrainingthe axis of the interconnecting pinion of said differential gearing 10from rotation about the axis of the opposed gears throughout theindividual strokes of reciprocation and intermittently releasing thesame to actuate said selector means for reversing stroke.

9. In mechanism for converting rotary motion to reciprocatory motion,the combination which includes, difierential gearing, unidirectionalrotary motion transmitting meansselectively operative with saiddifferential gearing for alternately driving through opposite sides ofthe same at dififerent speeds, at least two telescoping threaded membersrotatable each with one of said opposite sides of the differentialgearing and mounted for co-action to produce reciprocation, and selectormeans for engaging said unidirectional motion transmitting meansalternately to driving relation with said opposite sides of thedifferential gearing thus for producing alternately reversed anddifferently speeded strokes of reciprocation with said threaded members.

10. In mechanism for converting rotary motion to reciprocatory motion,the combination which includes, differential gearing, unidirectionalrotary motion transmitting means selectively connective with saiddifferential gearing for driving through axially opposite sides of thesame in alternately reversed directions, at least two telescopingthreaded members rotatable each with one of said opposite sides of thedifferential gearing and mounted for co-action to produce reciprocation,and selective means automatically setting said unidirectional motiontransmitting means alternately to driving relation with said oppositesides of the dififerential gearing thus for producing alternatelyreversed strokes of reciprocation with said threaded members.

ll. In mechanism for converting rotary motion to reciprocatcry motion,the combination which includes, differential gearing, including opposeddifferential gears and a pinion unidirectional rotary motiontransmitting means selectively operative with said differential gearingfor alternately driving opposite gears of the same in the samedirection, selective means for automatically engaging saidunidirectional rotary motion transmitting means alternately to drivingrelation with said opposite gears of the differential gearing and meansto lock the pinion against rotation about the axis of the gears whendriving either of them.

12. In mechanism for converting rotary motion to reciprocatory motion,the combination which includes, differential gearing comprising opposedgears and at least one interconnecting pinion for the same,unidirectional rotary motion transmitting means for selectively drivingthe differential gearing through said opposed gears, and means forrestraining the axis of said interconnecting pinion from rotation aboutthe axis of said gears and releasing the same only during selection ofthe driving relation between said unidirectional rotary motiontransmitting means and the difierential gearing.

13. The mechanism as defined in claim 3 in which means is provided torelease the axis of said pinion upon a predetermined stroke of thereciprocable threaded member.

14. The mechanism as defined in claim 4 in which each of the threadedmembers is formed in at least two parts telescopically andnon-rotatively secured together.

15. The mechanism as defined in claim 11 in which mechanism is providedto release the pinion during the change of drive.

16. The mechanism as defined in claim 15 in

